In an LTE (long term evolution) system, a minimum time interval for a base station (for example, eNB, Evolved NodeB) to schedule a user equipment (UE) is one subframe. For a UE that is scheduled in a subframe, a physical downlink control channel (PDCCH) of the UE is included in the subframe. A PDCCH may be a downlink scheduling grant (DL_grant) or an uplink scheduling grant (UL_grant). DL_grant or UL_grant sent by an eNB respectively carries scheduling information indicating a physical downlink shared channel (PDSCH) or scheduling information indicating a physical uplink shared channel (PUSCH). A PUSCH and a PDSCH may be considered as uplink and downlink data channels.
In an existing LTE system, one PDCCH can schedule PDSCH data of only one subframe. Specifically, a PDCCH and a scheduled PDSCH are located in the same subframe. For a frequency division duplexing (FDD) system, a UE feeds back uplink ACK/NACK (acknowledgement/non-acknowledgement) information corresponding to the PDSCH in a fourth subframe after this subframe, and for a TDD system, the UE feeds back uplink ACK/NACK information corresponding to the PDSCH in at least the fourth subframe after this subframe or later. The uplink ACK/NACK information may also be referred to as uplink feedback information in the following. A specific sequence of feedback is pre-configured, and a channel resource of the ACK/NACK is corresponding to a label of a control channel element (CCE) occupied by the PDCCH.
If the UE feeds back NACK, the eNB subsequently schedules a retransmission packet for the UE by using the PDCCH. The PDCCH carries new data indicator (NDI) information occupying one bit, so as to indicate whether a currently scheduled data packet is a new packet or an old packet. Specifically, if a value of an NDI bit is inconsistent with a previous NDI value, it indicates that the packet is a new packet; and if the value of the NDI bit is consistent with the previous NDI value, it indicates that the packet is an old packet. The PDCCH also carries a redundancy version (RV) number occupying two bits, which indicates four different versions.
In an LTE system of a subsequent evolved version, to improve scheduling efficiency of a PDCCH and reduce an overhead of the PDCCH, multi-subframe scheduling of the PDCCH is introduced, that is, one PDCCH may schedule PDSCHs of multiple subframes. In this case, multiple PDSCHs that are scheduled by one PDCCH each need to perform corresponding ACK/NACK feedback, and a current manner of determining a channel resource of the ACK/NACK feedback is no longer applicable.